title: Stability enhancement of cytochrome c through heme deprotonation and mutations.
abstract: The chemical denaturation of Pseudomonas aeruginosa cytochrome c(551) variants was examined at pH 5.0 and 3.6. All variants were stabilized at both pHs compared with the wild-type. Remarkably, the variants carrying the F34Y and/or E43Y mutations were more stabilized than those having the F7A/V13M or V78I ones at pH 5.0 compared with at pH 3.6 by ~3.0-4.6 kJ/mol. Structural analyses predicted that the side chains of introduced Tyr-34 and Tyr-43 become hydrogen donors for the hydrogen bond formation with heme 17-propionate at pH 5.0, but less efficiently at pH 3.6, because the propionate is deprotonated at the higher pH. Our results provide an insight into a stabilization strategy for heme proteins involving variation of the heme electronic state and introduction of appropriate mutations.
authors.affiliation: Graduate School of Biosphere Science, Hiroshima University, CREST of Japan Science and Technology Corporation, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8528, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Sonoyama
authors.forename: Jun
authors.initials: J
authors.lastname: Hasegawa
authors.forename: Susumu
authors.initials: S
authors.lastname: Uchiyama
authors.forename: Shota
authors.initials: S
authors.lastname: Nakamura
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sambongi
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics*; D045304:Cytochromes c / Q000737:chemistry* / Q000235:genetics*; D019791:Guanidine / Q000009:adverse effects; D006418:Heme / Q000031:analogs & derivatives / Q000737:chemistry*; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D009154:Mutation; D011489:Protein Denaturation; D055550:Protein Stability; D011522:Protons; D011550:Pseudomonas aeruginosa / Q000737:chemistry / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D011522:Protons; C081433:heme propionate-7; D006418:Heme; D045304:Cytochromes c; D019791:Guanidine